Product to promote fluid flow

ABSTRACT

A cellulose pulp particle having the shape of a general prismatoid having two parallel bases, the pulp particle comprising pulp fibers in a wet laid pulp sheet form, one of the bases having an area that is equal to or greater than the area of the other base, the area of the larger base being equal to or less than 35 mm 2  and equal to or greater than 8 mm 2 , the distance between the bases being equal to or greater than 0.9 mm and equal to or less than 5 mm, the particle being treated with a material. In some embodiments the material can be a hydrophilic, hydrophobic or softening chemical or a film.

The present invention relates to a product for improving flow of liquidsof all viscosities. More specifically, this invention is an inexpensiveand easily manufactured material that will provide improved bodily fluidand waste flow in a disposable, absorbent, sanitary article.

Absorbent or sanitary disposable articles such as diapers, adultincontinence products or sanitary napkins usually have anacquisition/distribution member against a storage member. These arehoused between a top sheet, which rests against the user and throughwhich fluid passes, and a backsheet which holds the liquid within theproduct and through which fluid does not pass. Theacquisition/distribution member receives fluid and distributes andtransfers the fluid to the storage member in which the fluid is held.The transfer should be fast enough so that fluid and other matter do notleak around the edges of the sanitary article or transfer back throughthe top sheet to the skin of the user.

The advantages and requirements of an acquisition/distribution member insanitary articles are well known in the art. Such members will rapidlyacquire and briefly contain low viscosity bodily fluids such as urineduring elimination where a relatively high volume of fluid on the orderof 50 ml or more is presented in a rather short time (on the order of 10sec to 1 minute) thereby preventing fluid leaks out of the article. Thismember will then provide for rapid fluid transfer to the rest of thearticle where the fluid is stored allowing itself to be available forrepeated fluid insults. To be successful this layer must providechannels that permit rapid flow even under a weight load caused by thewearer of article. It should be of low compressibility to maintain thesechannels but yet be flexible to provide comfort to the wearer. Inaddition, it is desirable for this member to maintain a relatively drytop layer to keep the skin of the wearer dry. One material used in suchacquisition/distribution members is crosslinked pulp fiber which willmaintain its bulk density when wet and under a load. Another is spunblown synthetic fibers.

Good management of higher viscosity fluids such as menses, loose stools,etc., has some additional requirements. Structures and/or materials thatmeet those requirements often will have features such as large voids toimmediately accumulate the high viscosity fluid. The surroundingstructure or material should then have the capability to absorb waterfrom the fluid thereby raising the viscosity of the high viscosity fluideven further to prevent leakage out of the article. The absorbed fluidshould then preferably migrate from this layer into the highly absorbentmaterials in the storage layer below. This structure and/or materialsmust still be moderately incompressible but flexible as described abovefor low viscosity fluid management.

The provision of these void spaces requires special designs of theacquisition/distribution layer and special equipment to form thesedesigns. This adds to the cost of the absorbent product.

Pulp is normally used in sanitary articles, but it is normally used infiber form. Pulp for use in the fiber form is usually supplied to thesanitary product plant as rolled sheets or flat cut sheets. Because ofthe simple production methods, pulp sheets are a highly economical formof pulp. The rolled sheet has a typical basis weight of 750 g/m² (gramsper square meter) and a caliper of 1.2 mm. (millimeters). The cut sheethas the same basis weight and is about 0.75 m (meter) by 0.76 m and acaliper of 1.2 mm. As explained later, the caliper and basis weight mayvary. The product is then shipped to manufacturers of sanitarydisposable products who then disintegrate the sheets into individualfibers. These fibers may be used in the acquisition/distribution memberor the storage member. The fibers give the sanitary products bulk,softness, and high absorbency. A typical pulp for sanitary articles isSouthern softwood pulp typically produced from Loblolly Pine and SlashPine, trees common in the Southeastern United States.

The sanitary article must be comfortable to the wearer, must acquirequickly, hold fluid and high viscosity material and must be unobtrusive.The acquisition/distribution member is important to obtaining theseresults by quickly acquiring and distributing the fluids from fluidmaterial and high viscosity material. There is a need for a simplesolution for an acquisition/distribution layer that may be used toacquire quickly and hold high viscosity fluids and normal fluids, beeasily produced, and be comfortable and unobtrusive when used in adisposable garment such as diapers, feminine hygiene products and adultincontinence products. The inventors have devised a simple solution thatprovides good acquisition and good distribution.

FIGS. 1-9 are isometric views of different embodiments of the invention.

FIG. 10 is an isometric view of the apparatus used for in-house loadedacquisition testing in Example 1.

FIG. 11 is a side view schematic of the layers of the commerciallyavailable diaper used in Examples 2 and 3.

Applicant realizes that some of the terms used in this application havedifferent definitions depending on the source. For example, thedefinitions found in Solid Mensuration, 2^(nd) Edition, by Willis F.Kern and James R. Bland, published by John Wiley and Sons, Inc., 1938,may not agree with the definitions found in The American HeritageDictionary of the English Language, 1979 edition, published by HoughtonMifflin, and neither may agree with the definitions found in Webster'sNew Collegiate Dictionary, 1973 edition published by G. and C. MerriamCompany. For this reason, applicant will use the following definitionsfor the terms being used in this application.

As used herein, the term “general prismatoid” is defined as a solidhaving at least one pair of sides that are “elements” of parallelplanes. These elements are referred to as the “bases” of the generalprismatoid. For the purposes of this application these elements aresurfaces. For the purposes of this application, a general prismatoiddoes not include spheres. For shapes that have more than one pair ofparallel sides, the bases will be defined as the pair of opposedparallel sides that are separated by the smallest distance.

As used herein, a “simple prismatoid” is a polyhedron having allvertices lying in one of two parallel planes. A polyhedron is a solidbounded by polygons. A polygon is a closed plane figure bounded by threeor more line segments. A simple prismatoid would include, for example,cubes, rectangular parallelepipeds, prisms, and pyramidal frustums. Forthe purposes of this application, a simple prismatoid is a type orsubset of a general prismatoid as defined herein.

As used herein, “cuboid” is synonymous with “rectangular parallelepiped”and is a polyhedron whose six faces are all rectangles. A cuboid is atype of simple prismatoid.

As used herein, the term “square cuboid” is defined as a cuboid with atleast one pair of opposite sides being squares. A square cuboid is atype of cuboid.

As used herein, “cylindrical surface” is a surface generated by a movingstraight line (“generator”) which is always parallel to a fixed line,and which always intersects a fixed plane curve (“directrix”) not in theplane with the fixed line. If the directrix of the cylindrical surfaceis a closed curve, the surface is “closed”. The directrix may be acircle, ellipse, flower shaped, or any irregular curve

As used herein, “cylinder” is a solid bounded by a closed cylindricalsurface and two parallel planes. A cylinder would be a type of generalprismatoid as defined herein.

As used herein, “right cylinder” is a cylinder where the cross sectionsall lie directly on top of one another. FIG. 3 illustrates an example ofa right cylinder.

As used herein, “right circular cylinder” is defined as a right cylinderwhere the bases are circular in shape. FIG. 2 illustrates an example ofa right circular cylinder. A right circular cylinder is a subset ofright cylinders.

As used herein, the term “height” refers to the perpendicular distancebetween the bases of a “general prismatoid” as defined herein.

The present invention relates to a product for improving flow of liquidsof all viscosities, especially urine, menses, and loose stools or feces.It is useful in absorbent or sanitary products such as diapers, femininecare products and adult incontinence products. It can be easily producedand exhibits improved acquisition properties.

In one embodiment the invention comprises particles which are generalprismatoids. In one embodiment the particles have small squares,circles, any other simple geometric shape, or even more complex shapesas at least one of the parallel bases of the general prismatoid. Inanother embodiment both of the bases of the particles have the sameshape. These general prismatoids have been cut, punched, or otherwiseshaped from a sheet of absorbent pulp. These parallel bases would be thesurfaces of the pulp sheet from which the particles are formed.

In manufacturing an absorbent article, it is usual for the back sheet tobe laid down, the storage core or member to be placed on top of the backsheet, the acquisition/distribution member to be placed on top of thestorage member and the top sheet to be placed on theacquisition/distribution member. There are usually many other elementsof the absorbent article which are placed on the article during itsmanufacture but the back sheet, storage member, acquisition/distributionmember and top sheet will only be considered here.

The back sheet is usually polyethylene or some other liquid imperviousmaterial. The storage member is usually pulp fibers into whichsuperabsorbent particles are placed. The pulp fibers and superabsorbentparticles are air laid onto the back sheet to form the storage member.The acquisition/distribution member would be placed on the layer of pulpfibers that comprises the storage core. The placement of theacquisition/distribution member will depend on the diaper design. Theacquisition/distribution member may be only in the area of the insultand transfer the insult to the storage layer and depend on the wickingcapability of the storage layer to move the fluid throughout the storagelayer. On the other hand the acquisition/distribution member may be overa larger area of the storage layer so that the wicking ability of theacquisition/distribution layer can be used to also spread the fluidthroughout the storage layer.

A top sheet is then placed over the acquisition/distribution member, andthe storage member and the top sheet and back sheet are adheredtogether. During this process pressure is placed on the article toadhere the top sheet and back sheet together and densify the article sothat it will have a narrow contour.

In forming the acquisition/distribution member, the particles would bedropped and scattered onto the storage layer over the required area toform the acquisition/distribution member.

In one embodiment the dimension of the shapes of the bases of theparticles would be larger than the thickness of the pulp sheet fromwhich they were produced. When scattered onto an absorbent article,particles with these dimensions will tend to orient themselves with thecut edges normal to the article and original pulp sheet surfacesparallel to the article. Misalignment of the pieces will be tend to becorrected during the finishing of the absorbent article where forcesnormal to the article are applied thereby realigning the cut pieces.

In another embodiment, the particles can be surface treated withchemicals to modify the absorptive properties or flow properties, in apositive or negative way. The pulp sheet can be surface treated beforemanufacture of the particles. The faces of the particles can be treatedwith hydrophobic or hydrophilic chemicals. A hydrophilic surfacetreatment will increase the absorption and retention of fluid in theparticle. A hydrophobic treatment will increase fluid flow through theacquisition/distribution member. A softening chemical will providecomfort to the user of an article incorporating the particles. In oneembodiment, one base of the particle could be treated with a hydrophilicchemical and the other base treated with a hydrophobic chemical toobtain the attributes of both of these treatments. These treatmentswould be placed on the pulp sheet prior to forming particles from thepulp sheet. The chemicals could be placed on the pulp sheet by atransfer roll such as a size press. Hydrophilic chemicals that can beused are glycerol, corn syrup, sugar, calcium chloride, magnesiumchloride, poly glycols, sorbitol, and many others. Hydrophobic chemicalsthat can be used are styrene acrylic esters, styrene acrylic acids,fluoro-compounds, alkyketene dimer, and many others. Other chemicalsthat could be added to make the surfaces hydrophobic are starch andpolyvinyl alcohol among others. Addition rates could be as low as 0.01pounds per ton and as high as 100 pounds per ton.

When chemicals are placed on the surfaces of the pulp sheet, which willbecome the bases of the particle, the chemical will penetrate into thesheet for some distance, depending on the fiber being used, the densityof the sheet, the amount of chemical and the pressure with which thechemical is applied. The chemicals can be sprayed or coated onto thesheet before or after drying.

The pulp sheet may be treated during manufacture. The chemicals can beadded to the process during sheet manufacture and before drying. Thelocation of addition will depend on the chemical. A chemical that can bewashed out with the water will be placed in the sheet late in theprocess. A chemical that will not be washed out with the water can beplaced in the sheet earlier in the process. In some instances ahydrophilic chemical may be added to the pulp sheet during manufactureand a hydrophobic chemical placed on the surface of the pulp sheet priorto the formation of the particles.

In a further embodiment the particles can be treated with otherchemicals to enhance other performance or aesthetic or comfortattributes. The pulp sheet can be treated before manufacture of theparticles or the particles can be treated after manufacture. Chemicalsthat add hydrophobicity will allow for faster acquisition rates.Chemicals that add hydrophilicity will allow for great absorbency, fluidcapacity, and dewatering capability. Dyes may be added to modifyappearance. Softening chemicals may be added for comfort. Typicalsoftening agents are sorbitol and glycerin.

In additional embodiments the particles may include polymer films,adhesives, more than one layer of pulp or other materials such asdifferent fibers or chemically modified fibers. The pulp sheet can becombined with other materials such as polymer films, adhesives,additional pulp sheets, or other materials before manufacture of theparticles. Different fibers or chemically modified fibers could be usedin the production of the pulp sheet. Any of these can modify performanceparameters of the final particles. High bulk fibers, both cellulosic andpolymeric, could be added to raise the bulk of the particle to providesome softness. Hydrophobic fibers, both cellulosic and polymeric, couldbe added to modify the acquisition rate and fluid retention capacity ofthe final particles. Films such as polyethylene, nylon or PET can bebonded to the pulp sheet prior to forming into particles.

The pulp particles are manufactured from a pulp sheet. The pulp sheet iswet laid and there will be a random orientation of the fibers. Thefibers will tend to align primarily along the machine direction of thesheet and to a slightly lesser extent along the cross direction of thesheet. There is some alignment along the direction normal to the facesof the sheet, commonly named the z-direction. In a wet laid pulp sheetthe fibers attach to each other by hydrogen bonding.

Southern pine fibers are used as absorbent fibers because they tend tohave a large bore and higher stiffness than other fibers, which lead toits high fluid absorbency. This fiber morphology combined with thetypical fiber orientation means there will be greater expansion of theparticle when a southern pine fiber is used.

Several embodiments of the present invention are illustrated in thedrawings.

FIG. 1 is an isometric view of an embodiment of the present inventionshowing a “general prismatoid” having square shaped bases in which 1 ais the cut edge of the particle and bases 1 b are the surfaces of theoriginal pulp sheet from which this particle was formed. The squareshaped base is exemplary. The base may be rectangular, have undulatingedges or jig-saw shaped edges. It may have any number of cut sides. Itmay have 3 up to ten or more sides. It may be a general prismatoid, asimple prismatoid, a cuboid or a square cuboid. The planes of the basesare substantially parallel because they are the surfaces of the originalpulp sheet.

FIG. 2 is an isometric view of a second embodiment of the presentinvention showing a cylindrical particle in which 2 a is the cut edge ofthe particle and bases 2 b are the surfaces of the original pulp sheetfrom which this particle was formed. The edges of the bases are shown ascircular. Again this is exemplary. The edges can be any continuousshape. Among other shapes it may be a general cylinders a right generalcylinder or a right circular cylinder. These specified shapes are notlimiting but only given as examples. The planes of the bases aresubstantially parallel because they are the surfaces of the originalpulp sheet.

FIG. 3 is an isometric view of a third embodiment of the presentinvention showing cylindrical particle in which 3 a is the cut edge ofthe particle and base 3 b is the surface of the original pulp sheet fromwhich this particle was formed. This exemplifies a cylindrical particlein which the edges of the bases are other than a circle. The edges areshown as flower shaped. This shape is not limiting but only given as anexample. The planes of the bases are substantially parallel because theyare the surfaces of the original pulp sheet.

FIG. 4 is an isometric view of a fourth embodiment of the presentinvention showing a general prismatoid particle cut from a material inwhich two pulp sheets 4 a and 4 b are adhered together with an adhesive4 c. The outer surfaces of the sheets 4 a and 4 b form the bases of thegeneral prismatoid. It may be a general prismatoid, a simple prismatoid,a cuboid or a square cuboid. These shapes are not limiting but onlygiven as examples. In the drawing the edges of the bases form a square.The square shaped base is exemplary. The base may be rectangular, haveundulating edges or jig-saw shaped edges. It may have any number of cutsides. It may have 3 up to ten or more sides. The planes of the basesare substantially parallel because they are the surfaces of the originaladhered pulp sheets. The two pulp sheets are exemplary. Two or more pulpsheets may be adhered together.

FIG. 5 is an isometric view of a fifth embodiment of the presentinvention showing a general prismatoid particle 5 b cut from a pulpsheet and having on one base a lamination film 5 a and on the other basea lamination film 5 c. The lamination films are exemplary of treatingthe bases of the particle with either a film or a chemical such as ahydrophilic or hydrophobic chemical. The laminations or treatmentchemicals would be placed on the pulp sheet prior to the manufacture ofthe particles. The films could be either heat laminated or adhered tothe pulp sheet. It may be a general prismatoid, a simple prismatoid, acuboid or a square cuboid. In the drawing the edges of the bases form asquare. These shapes are not limiting but only given as examples. Thesquare shaped base is exemplary. The base may be rectangular, haveundulating edges or jig-saw shaped edges. It may have any number of cutsides. It may have 3 up to ten or more sides. The planes of the basesare substantially parallel because they are the surfaces of the originalpulp sheet.

FIG. 6 is an isometric view of a sixth embodiment of the presentinvention showing a cylindrical particle 6 b cut from a pulp sheet andhaving on one base a lamination film 6 a and on the other base alamination film 6 c. The lamination films are exemplary of treating thebases of the particle with either a film or a chemical such as ahydrophilic or hydrophobic chemical. The laminations or treatmentchemicals would be placed on the pulp sheet prior to the manufacture ofthe particles. The films could be either heat laminated or adhered tothe pulp sheet. Among other shapes it may be a cylinder, a right generalcylinder or a right circular cylinder. These specified shapes are notlimiting but only given as examples The edges of the bases are shown ascircular. Again this is exemplary. The edges can be any continuousshape. The planes of the bases are substantially parallel because theyare the surfaces of the original pulp sheet.

FIG. 7 is an isometric view of a seventh embodiment of the presentinvention showing a general prismatoid particle cut from two pulp sheets7 a and 7 b adhered together with an adhesive 7 c and having alamination film 7 d on one base and a lamination film 7 e on the otherbase. The lamination films are exemplary of treating the bases of theparticle with either a film or a chemical such as a hydrophilic orhydrophobic chemical. The laminations or treatment chemicals would beplaced on the pulp sheets prior to the manufacture of the particles. Thefilms could be either heat laminated or adhered to the pulp sheet. Itmay be a general prismatoid, a simple prismatoid, a cuboid or a squarecuboid. These shapes are not limiting but only given as examples. In thedrawing the edges of the bases form a square. The square shaped base isexemplary. The base may be rectangular, have undulating edges or jig-sawshaped edges or have a single unitary edge of any shape such as a circleor ellipse or flower shaped. It may have any number of cut sides. It mayhave 3 up to ten or more sides. The planes of the bases aresubstantially parallel because they are the surfaces of the originalpulp sheets.

FIG. 8 is an isometric view of an eighth embodiment of the presentinvention showing a general prismatoid particle formed from the portionof the pulp sheet left over after the general cylindrical particles havebeen cut from a pulp sheet. It is the section between 4 tangentialcylindrical portions and is formed of four concave surfaces 8 a thatmeet at points 8 c. A base 8 b is also shown. The shape of the concavesurfaces will depend on the particular shape of the cylinders.

FIG. 9 is an isometric view of an ninth embodiment of the presentinvention showing a general prismatoid particle formed from the portionof the pulp sheet left over after the general cylindrical particles havebeen cut from a pulp sheet. It is the section between 4 cylindricalportions that are spaced from each other. and is formed of four concavesurfaces 9 a that are joined at their ends by planes 9 c. A base 9 b isalso shown. The shape of the concave surfaces will depend on theparticular shape of the cylinders.

These embodiments are exemplary of the shapes and types of particlesthat can be formed. It should be understood that any of the particleshapes may be made of more than one ply and may be treated as describedherein.

The bases of the particle may have the same or different areas. The areaof the largest base, if the bases have different areas, or of a base, ifthe bases have the same area, will be equal to or less than 35 mm² andequal to or greater than 8 mm². Although square particles are shown, thelength can be greater than the width. The thickness or height of theparticle will be from 0.9 to 1.5 mm if the particle is a singlethickness particle, from 1.8 mm to 3 mm if the particle is a doublethickness particle, and from 2.7 mm to 4.5 mm if the particle is atriple thickness particle. The height can be as high as 6 mm. Asdescribed above the dimension of the base of the particle should begreater than the thickness of the particles so that the particles willlie on their bases in the absorbent article. As described below thethickness of a pulp sheet has a maximum dimension so there may be two ormore thicknesses of pulp in some embodiments.

The dimensions of the particle must be small if they are being used inan absorbent article such as a diaper, a feminine care product or anadult incontinent product. They must lie down within the garment and beform fitting to the contours of the body. They must provide comfort tothe wearer. A large particle will not provide these attributes. Alsothey must be able to distribute evenly. Smaller particles will tend todistribute more evenly than large particles. It has been found that thesmaller particles will absorb more quickly in repeated insults ascompared to larger particles. This can be seen in the examples. It hasalso been found that round particles absorb more quickly in repeatedinsults than square or rectangular particles. This can also be seen inthe examples. The particles cannot be too small or they will not layright in the absorbent article.

These particles are formed from pulp sheets or enhanced pulp sheets. Inpractice a pulp sheet made from any pulp may be used.

The raw material for pulp may be any hardwood or softwood or othermaterial commonly used for pulp, such as bagasse. It may be made from achemical, mechanical, thermomechanical or chemithermomechanical process.In one embodiment a kraft pulp made from southern U.S. softwoods may beused. In another embodiment a kraft pulp made from southern U.S. pine,such as loblolly pine, may be used.

A chemical pulp is manufactured by cooking the raw material in an alkalisuch as sodium hydroxide. The hydroxide may be combined with a sulfateto manufacture kraft pulp. The hydroxide may be combined with a sulfiteto manufacture sulfite pulp. In the cook the lignin and hemicelluloseare solubilized and separated from the cellulose. The yield of the pulpwill depend on the amount of lignin and hemicellulose removed. Usuallymore hemicellulose and lignin is removed in sulfite pulping than insulfate pulping. The hemicellulose and lignin are washed from the pulpand the pulp is then brightened with oxidizing agents by bleaching.Chlorine dioxide and chlorine are typically used as bleaching agents.

A mechanical pulp is manufactured by grinding the raw material intofibers. The lignin and hemicelluloses in the raw material will for themost part remain with the fiber.

A thermomechanical pulp is manufactured by steaming the raw material andthen grinding the raw material into fibers. The steam softens the rawmaterial and makes it easier to grind into fibers. The steam may removesome of the hemicellulose and lignin from the fiber during the process.

A chemithermomechanical pulp is manufactured by treating the rawmaterial with chemicals and steam and then grinding the raw materialinto fibers. The chemicals and steam may remove some of thehemicellulose and lignin from the fibers.

The process, after forming the fibers, is the same for any of thefibers. The fibers are slurried in water and the slurry of fibers andwater is flowed onto a moving screen. The purpose of the rest of theprocess is to remove water from the fibers and to cause the fibers toform into a self-supporting web, either by hydrogen bonding between thefibers in the case of chemical pulp, or by intertwining and hydrogenbonding in the case of mechanical, thermomechanical andchemithermomechanical fibers.

Water is removed from the fibers as they pass along the screen. Thefibers are then calendered between rolls to further remove water and topress the fibers together. The fibrous web is then passed to a drier tofurther remove water. The drier can be a through air drier or a steamheated can drier. In any case, the pulp mat must be thin enough to bethoroughly dried. Because of the requirements of the process, the pulpmat will have a thickness of from 0.9 mm to 1.5 mm. A typical pulp matcan have a thickness of 1.2 mm.

In the wet end of the pulp process, hydrophilic chemicals can be addedto the pulp. These chemicals will remain in the pulp sheet.

The thickness of the pulp mat will dictate the number of thicknesses inthe particle.

The basis weight of the pulp sheet can also vary because of the pulpbeing used and the manufacturing techniques. It may vary from 600 g/m²to 1000 g/m².

The pulp sheet can be used as is for the manufacture of the particles orit can be adhered to another pulp sheet to form a double thickness pulpsheet. It can also be adhered to other pulp sheets to form multiplethickness pulp sheets before the manufacture of the particles. The outersurface of the pulp sheet or sheets may be treated in a size press orother apparatus to apply material to the sheet. It may also have filmlaminated to its outer surface.

In commercial practice the particles would be formed by cutting theparticles out of the pulp sheets or laminated pulp sheets using a rotarydie cutter having the required particle shape and size, or by othercutting devices known in the art.

The pulp sheet used for the particles in the examples below iscommercially available Weyerhaeuser Columbus Pine pulp manufactured inColumbus, Miss. It contained only pulp fibers and contained no modifiedfibers or other types of fibers.

The adhesive used for adhesive laminations in the examples was a 2″ widecommercial splicing tape, product number AR7418 CO#E5863, produced byAdhesive Research Inc., Glen Rock, Pa. This tape has an adhesive on bothsides. The adhesive on one side is attached to a removable backing. Inpractice any adhesive that will adhere two sheets of pulp together maybe used. It may be in sheet form or may be a liquid that can be coatedon the pulp sheet by brush, roll or curtain coating. In any embodimentthe adhesive must coat the entire surface of a roll so that the pulpportions forming the particles taken from the adhered rolls will beadhered together.

The adhesive laminated pulp sheet used in the examples was produced byapplying strips of the Adhesive Research adhesive tape described aboveto one side of a pulp sheet. The strips were laid side-by-side until thewhole surface of the pulp sheet had the adhesive strips adhered to it.The tape backing was removed thereby exposing the other adhesive layer.A second pulp sheet was then pressed onto the first sheet resulting inthe adhesive lamination of the two sheets. In practice the adhesivewould be applied to one surface of a pulp sheet. The adhesive could betwo sided adhesive material, or a liquid adhesive that is spread orsprayed or curtain coated onto the surface of the pulp sheet. Theadhesive may be spread by a roll coater or other type of coater. Anothersheet of pulp would be placed on the first sheet of pulp and the twosheets adhered together. The process would be repeated if a three plypulp sheet were to be used.

The lamination film used to produce the laminated pulp sheet was a 3.0mil Doculam CR film available from Binder Products, Seattle, Wash. Theyare composed of general purpose polyesters. The laminator used was amodel BA-PS27 made by Banner American Products, Inc., Rancho California,Calif.

Pulp sheets having film laminated to their bases were produced byfeeding the pulp sheet into the Banner American laminator at a speedsetting of 10, roll temperatures of 325° F., top and bottom, and maximumpressure with the Doculam lamination film on the top and bottom unwinds.The pulp sheet had film laminated to its top and bottom surfaces. Pulpsheets adhered together to form a two ply sheet had film laminated totheir bases in the same manner.

In practice any type of laminating film may be used to provide a film onthe exterior outer bases of the particles. The laminating films may beadhered by heat or by an adhesive.

Twelve types of particles were provided for the examples.

Particle 1 was a square cuboid as shown in FIG. 1. It was 3 mm long, 3mm wide and the perpendicular distance between the bases was 1.2 mm. Theareas of the bases of a particle were equal and the area of each basewas 9 mm². The particles were cut from a single thickness pulp sheetwith a conventional paper cutter. The particles had no surface coatingor lamination.

Particle 2 was also a square cuboid as shown in FIG. 1. It was 5 mmlong, 5 mm wide and the perpendicular distance between the bases was 1.2mm. The areas of the bases of a particle were equal and the area of abase was 25 mm². The particles were punched from a single thickness pulpsheet using a hand paper punch produced by Fiskars, item 23587097. Theparticles had no surface coating or lamination.

Particle 3 was a square cuboid as shown in FIG. 4. It was 5 mm long, 5mm wide and the perpendicular distance between the bases was 2.4 mm. Theareas of the bases of a particle were equal and the area of a base was25 mm². The particles were cut from a double thickness pulp sheet. Thedouble thickness pulp sheet was formed by adhering two pulp sheetstogether as described in the above description of forming a doublethickness pulp sheet. The particles were cut using a conventional papercutter. The particles had no surface coating or lamination.

Particle 4 was a square cuboid as shown in FIG. 5. It was 5 mm long, 5mm wide and the perpendicular distance between the bases was 1.2 mm. Theareas of the bases of a particle were equal and the area of a base was25 mm². The particles were cut from a single thickness pulp sheet usinga conventional paper cutter. The particle had a PET surface laminationon both bases.

Particle 5 was a square cuboid as shown in FIG. 7. It was 5 mm long, 5mm wide and the perpendicular distance between the bases was 2.4 mm. Theareas of the bases of a particle were equal, and the area of a base was25 mm². The particles were cut from a double thickness pulp sheet. Thedouble thickness pulp sheet was formed by adhering two pulp sheetstogether as described in the above description of forming a doublethickness pulp sheet. The particles were cut using a conventional papercutter. The particle had a PET surface lamination on both bases.

Particle 6 was a right circular cylinder as shown in FIG. 2. It had adiameter of 3 mm and the perpendicular distance between the bases was1.2 mm. The areas of the bases of the particle were equal and the areaof a base was 7 mm². The particles were punched from a single thicknesspulp sheet using a Fiskars punch, item 23517097. The particles had nosurface coating or lamination.

Particle 7 was a right circular cylinder as shown in FIG. 2. It had adiameter of 6 mm and the perpendicular distance between the bases was1.2 mm. The areas of the bases of the particle were equal and the areaof a base was 28 mm². The particles were punched from a single thicknesspulp sheet using a Fiskars punch, item 23527097. The particles had nosurface coating or lamination.

Particle 8 was a right flower shaped cylinder as shown in FIG. 3. Theperpendicular distance between the bases was 1.2 mm. The bases had thesame area and each base had a cross sectional area of 26 mm². Theparticles were punched from a single thickness pulp sheet using aFiskars punch, item 23627097. The particles had no surface coating orlamination.

Particles 1A, 2A, 6A, and 7A, are PET surface lamination versions ofparticles 1, 2, 6, and 7 respectively.

FIG. 9 is an isometric view of the apparatus used for in-house loadedacquisition testing in Example 1. A cylinder 9 a is attached to a squareplate 9 b. The lower half of the apparatus 9 c is a matching plate to 9b.

FIG. 10 is a side view schematic of the layers of the commerciallyavailable diaper used in Examples 2 and 3. The outside of the diaper isthe backsheet 10 a. A tissue 10 b lies on top of the backsheet 10 a andunderneath the fluff and SAP storage core or member 10 c. On top of thestorage core 10 c is another tissue layer 10 d. On top of the tissuelayer 10 d is an acquisition patch 10 c, and on top of the acquisitionpatch 10 e is a top sheet 10 f which is in contact with the wearer'sskin.

The fluff pulp used in the specially made pads was commerciallyavailable Weyerhaeuser NB416, manufactured in New Bern, N.C. It wasfiberized on a Fitz Hammer Mill, model DAS06, milled with a fixed hammerrotor, at 10,000 rpm, with a breaker bar gap of 3 mils, with a feed rateof about 50 g/minute, with no screen.

The topsheet used in the specially made pads in the examples was aspunbond polyester web, with a basis weight of 15 gram per square meterand a caliper of 1.8 mm, commercially available from First QualityNonwovens Inc, product #SB1501810.

The tissue used in the specially made pads in the examples was producedby Cellu Tissue Holdings, Alpharetta, Ga., grade 32201-1, with a basisweight of 18 g/m².

EXAMPLE 1

The experimental pads for Example 1 below were produced as follows. Sixinch diameter pads containing these pulp sheet particles were made asfollows. A mass of 4.0 grams of fiberized NB416 and 1.0 gram of Hysorb8600 superabsorbent were fed into a six inch airlaid pad former andairlaid onto an 8 inch square of tissue. This resulted in a 5.0 gramairlaid pad with a basis weight of 274 grams per square meter, notincluding the tissue. Production of such airlaid pads is well known inthe art. The airlaid pad was then laid onto an 8 inch square of blotterpaper for conveyance. An additional 5.0 grams of additional NB416 fluffwas evenly placed on top of the pad for the control pad, and 5.0 gramsof pulp particles were evenly placed on top of the other pads. A 6 inchcircle of tissue was placed directly on top of the pads. The pad wasthen placed into a square plastic mold with a 6 inch circular cylindercut of the center. An 8 inch square of top sheet was then laid on top ofthe mold. A matching 6 inch circular plug was then placed into thecenter of the mold on top of the pad resulting in the corners of the topsheet extending out beyond the plug. Two small 0.5 mm thick metal shimswere placed on top of the square mold on opposite corners. The mold andits contents were then put between two 12 inch square aluminum platesand compressed at force of 7 tons on a Wabash hydraulic press, model125-15-SIMX, manufactured by Wabash MPI, Wabash, Ind. The moldsurrounding the pad was removed, and the corners of the topsheet weresmoothed back down. The caliper of the pad was measured. If the pad wasnot in the target caliper range of 2.40-2.60 mm, the compressionprocedure was repeated until the target caliper was achieved.

The acquisition test frame was manufactured in-house and is shown inFIG. 9. It can be described as follows. A Plexiglas tube of a 6 inchheight, an outer diameter of 1.5 inches, and an inner diameter of 1.125inches is permanently attached to the center of a 10 inch squarePlexiglas plate. The plate is 5 mm thick with a 1.125 inch hole cut outof the center. This top plate and tube together weigh 425.55 g. Thebottom plate is also a 10 inch square, 5 mm thick, but with no holes.

The compressed pads were then placed and carefully centered on thebottom plate of the acquisition test frame, and the blotter paper wascarefully removed. The top plate was then carefully centered and placedon top of the pad and the bottom plate. One 125 gram weight was thenplaced onto each of the four corners of the top plate, with the centerof the weight located 1 inch from the two sides forming the corner. Asmall funnel with a delivery spout of 5 mm in diameter was placed insidethe tube on the top plate with the bottom of the funnel being 2⅞ inchesabove the top surface of the pad. Thirty milliliters of synthetic urinewas quickly poured in the funnel and a stopwatch started. The stopwatchis stopped when the meniscus of the synthetic urine falls below thebottom of the tube in the top plate. This time is the acquisition timefor the “first insult” and was recorded in seconds. A second stopwatchwas started when the first one was stopped. When 20 minutes had elapsedon the second stopwatch, the insult procedure was repeated with a second30 milliliter dose in exactly the same manner with the recorded timebeing the second insult time. After another waiting period of 20minutes, a third 30 milliliter dosage was added in exactly the samemanner with the recorded time being the third insult time. Theacquisition rate was calculated by taking the insult volume, 30 ml, anddividing by the individual acquisition times. The results for a fluffcontrol and particles 1 through 8 are shown in Table 1.

TABLE 1 Loaded Acquisition Rate (ml/sec) Number 1st 2^(nd) 3^(rd) ofInsult Insult Insult Sample Tests ave s.d. ave. s.d. ave. s.d. NB416 61.3 0.1 1.6 0.1 1.7 0.1 Fluff Particle 1 3 2.1 0.2 4.0 0.3 3.8 0.3Particle 2 1 1.4 — 2.4 — 2.3 — Particle 3 3 2.4 0.0 6.1 0.7 6.6 0.3Particle 4 3 1.8 0.2 3.6 0.4 3.6 0.3 Particle 5 3 2.6 0.4 5.9 0.7 6.50.4 Particle 6 3 2.2 0.1 4.2 0.7 4.1 0.4 Particle 7 3 1.8 0.1 2.7 0.12.5 0.3 Particle 8 1 1.9 — 3.5 — 3.3 —

For absorbent products, a fast acquisition is preferable since thisindicates that the fluid expressed is rapidly taken up into the productand there is less chance of leakage and would give a more comfortablefeeling to the user since the article would feel dryer on the skin. Inevery case, the particles performed better than an equivalent weight offluff. The adhesive laminated particles, particles #3 and #4, showed thebest acquisition times. It is believed that during the insult, theparticles swelled causing a larger void for the insulting liquid to passmore freely. In terms of cross sectional area, the smaller particlesperformed better. Three mm circles were better than 5 mm circles, and 3mm squares were better that 4 mm squares. In general, circles seemedbetter than squares.

EXAMPLE 2

The diapers used for Example 2 and Example 3 were obtained commercially.A cross section of the diaper is shown in FIG. 9. The layers of thediaper, starting from the skin contact side are: nonwoven topsheet, highloft nonwoven acquisition layer, tissue, fluff and SAP (superabsorbent)storage core, tissue, and a polymer film-nonwoven laminate. The diaperhad a foam type waistband with Velcro fasteners and 2 elastic legstrands and 2 elastic inter-leg gather strands. The backsheet was awhite, breathable, nonwoven lamination. The entire diaper weighed 40grams, with the fluff core weighing 12.6 g, the SAP weighing 10.9 g, theacquisition layer weighing 0.23 g. The entire diaper was 47 cm inlength, 38 cm wide in the back, 28 cm wide in the front, and 23 cm atits narrowest point. The acquisition layer was 16 cm in length, 5 cm inwidth, resulting in a basis weight of 30 g/m². The fluff and SAP corewas 40 cm in length, and a uniform 12 cm in width.

In sample 1, the diapers were used as is for the tests. In sample 2, thesides of the top sheet were cut along the side edge of the diaper,pulled back, replaced, and resealed with a hot air gun as a control forthe diapers using particles. In sample 3, the sides of the top sheetwere cut along the side edge of the diaper and the acquisition layer wasremoved. In examples 4-6 the sides of the top sheet were cut along theside edge of the diaper and the acquisition layer removed and replacedwith particles of the type shown in the Table 2 in the amount shown inTable 2. In samples 3-6, the topsheet was replaced in the same manner assample 2.

The diapers were tested for loaded acquisition times on an Anarewet Plustester, obtained from Courtray Consulting, Douai, FRA. The basicoperating procedure is as follows. Up to three diapers or test specimensare placed on top of a flat inflatable rubber bladder and a thickplastic plate is placed on top. The rubber bladder is inflated to thedesired pressure. An aliquot of the desired fluid is automatically addedto the insult point of the specimen and the time it takes to be fullyabsorbed into the diaper is electronically measured. After a specifiedpause, the insult procedure is repeated, followed by an additional pauseand insult.

For both Examples 2 and 3 the insult point was 0.75 inches from thefront edge of the acquisition patch. The front edge of this patch wasapproximately 5 inches from the front edge of the diaper. The pressureapplied to the diaper was 10 mb. The volumes of the three insults were60 ml each, and the pauses between the insults were 300 seconds. In thismanner the loaded acquisition times were obtained and are listed intable 2.

TABLE 2 Loaded Acquisition Time Weight (sec) of Particles or 1st 2nd 3rdAcquisition Acquisition Layer Insult Insult Insult Total Sample Layer(g) ave s.d ave. s.d ave. s.d ave. s.d. 1 As is 0.23 17 1 39 6 64 11 11917 2 As is but 0.23 20 3 43 7 68 13 130 22 opened 3 Removed 0 22 1 50 485 9 158 14 4 Particle 1 2.0 16 2 32 2 51 2 100 6 5 Particle 1 0.5 22 347 11 76 19 144 33 6 Particle 3 2.0 12 1 19 2 60 6 91 8As show in the table, opening and reclosing the diaper increases theacquisition time slightly. This is a known phenomenon due to thedisruption of the contact between the top sheet and the acquisitionlayer. The higher the level of contact there is, the faster theacquisition is. The table also shows that completely removing theacquisition layer raises the acquisition times substantially asexpected. Replacing the acquisition layer with 2.0 gram of particle type1, lowered the acquisition time by about 25% when compared to thecontrol, “as is but opened” diaper. When the acquisition layer wasreplaced with only 0.5 g of particle 1, the acquisition time wasslightly more than the “as is but opened” control diaper. When theacquisition layer was replaced with 2 grams of particle type 3, thedouble thick particle, the acquisition time drops about 30% whencompared to the “as is but opened” control diaper. Because of thesignificantly higher basis weight of the particles compared to the highloft acquisition layer, a significantly higher total weight of particleshad to be added to get a reasonable coverage, since each particleweighed on the order of 0.01-0.03 grams.

EXAMPLE 3

Example 3 illustrates another experiment run in an exactly same manneras Example 2 on the Anarewet tester. Table 3 shows the results ofexperiment.

TABLE 3 Weight of Loaded Acquisition Particles or Time (sec) AcquisitionNumber 1st 2^(nd) 3rd Sam- Acquisition Layer of Insult Insult InsultTotal ple Layer (g) Obs. ave. ave. ave. ave. 1 As it but 0.3 1 24 49 78151 opened 2 Particle 2A 2.2 1 15 30 46 91 3 Particle 1A 2.2 1 13 20 3063 4 Particle 5 2.2 1 8 9 12 29 5 Particle 7A 2.2 1 16 29 15 60 6Particle 6A 2.2 1 13 19 25 57 7 Particle 8 2.0 1 15 25 39 79

Samples 2-6 are all PET laminated particles of various shapes whereparticle 5 is also an adhesive laminated, double thick particle. Sample1, the control, is reasonably close to the identical control in Example2. Changes in ambient temperature and humidity can affect theacquisition time, and diapers do have a natural variability betweenthem. The same trends appear in Example 3 as Example 2. Smaller circlesand squares show an improvement with lower acquisition times than largerones, and circles generally have a lower acquisition time than squares.When comparing PET laminated particles to non-laminated particles, onecan see a sharp drop in the laminated particles acquisition time. Forparticle 1 a, which is a laminated square, when compared to particle 1,which is the same square but not laminated, shows a 37% drop in totalacquisition time. For particle 5, which is the laminated version ofparticle 3, an adhesive laminated double thick square, the drop is 73%.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

1. A cellulose pulp particle having the shape of a general prismatoidhaving two parallel bases, the pulp particle comprising pulp fibers in awet laid pulp sheet form, one of the bases having an area that is equalto or greater than the area of the other base, the area of the largerbase being equal to or less than 35 mm² and equal to or greater than 8mm², the height being equal to or greater than 0.9 mm and equal to orless than 6 mm, the particle being treated with a material.
 2. Theparticles of claim 1 in which at least one of the bases is treated withthe material.
 3. The particle of claim 2 in which the material isselected from hydrophilic, hydrophobic and softening materials.
 4. Theparticle of claim 1 in which the material is a film, and at least one ofthe bases is coated with the film.
 5. The particle of claim 1 in whichthe material is selected from hydrophilic, hydrophobic and softeningmaterials and is throughout the fibers.
 6. The particle of claim 5 inwhich at least one of the bases is treated with a material differentfrom the material that is throughout the fibers.
 7. The particle ofclaim 1 in which the general prismatoids is selected from simpleprismatoids, cuboids, and square cuboids.
 8. The particles of claim 7 inwhich at least one of the bases is treated with the material.
 9. Theparticle of claim 8 in which the material is selected from hydrophilic,hydrophobic and softening materials.
 10. The particle of claim 7 inwhich the material is a film, and at least one of the bases is coatedwith the film.
 11. The particle of claim 7 in which the material isselected from hydrophilic, hydrophobic and softening materials and isthroughout the fibers.
 12. The particle of claim 11 in which at leastone of the bases is treated with a material different from the materialthat is throughout the fibers.
 13. The particle of claim 1 in which thegeneral prismatoids is selected from general cylinders, right generalcylinders and right circular cylinders.
 14. The particles of claim 13 inwhich at least one of the bases is treated with the material.
 15. Theparticle of claim 14 in which the material is selected from hydrophilic,hydrophobic and softening materials.
 16. The particle of claim 13 inwhich the material is a film, and at least one of the bases is coatedwith the film.
 17. The particle of claim 13 in which the material isselected from hydrophilic, hydrophobic and softening materials and isthroughout the fibers.
 18. The particle of claim 17 in which at leastone of the bases is treated with a material different from the materialthat is throughout the fibers.